Air conditioning system

ABSTRACT

An air conditioning system includes: a burner unit having a burner and a first casing housing the burner and having an air inlet; and a heat exchanger unit having a heat exchanger through which flammable refrigerant passes, a second casing housing the heat exchanger, and a connection portion connected to a refrigerant connection pipe extending from a heat source unit. The first casing has a first surface, the second casing is disposed to overlap a part of the first surface, the first surface includes a first portion that overlaps the second casing and a second portion not overlapping the second casing. The connection portion is disposed in the second casing to project onto the second portion of the first casing. The air inlet is provided on a surface that is other than the second portion and is at least one of a plurality of surfaces adjacent to the first surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT International Application No. PCT/JP2021/007353, filed on Feb. 26, 2021, which claims priority under 35 U.S.C. 119(a) to Patent Application No. 2020-032295, filed in Japan on Feb. 27, 2020, all of which are hereby expressly incorporated by reference into the present application.

TECHNICAL FIELD

The present disclosure relates to an air conditioning system in which a gas burner is disposed upstream side of a heat exchanger.

BACKGROUND ART

Conventionally, a furnace-equipped duct split-type air conditioner in which an indoor unit is installed in an attic, a basement, a garage, a closet, or the like is widely known. For example, in an air conditioner as disclosed in Patent Literature 1 (JP 2015-145764 A), a heat exchanger constituting a part of a refrigerant circuit and a gas burner are disposed in the same duct, and the gas burner is located upstream of the heat exchanger.

SUMMARY Technical Problem

In a case where a refrigerant flowing through the refrigerant circuit is a flammable refrigerant, in preparation for a refrigerant leak from a connection portion connecting the heat exchanger and a refrigerant connection pipe, a leakage detection sensor detects the refrigerant leak early for safety, and thorough measures are taken. The present application aims to further improve safety.

An air conditioning system according to a first aspect includes a burner unit and a heat exchanger unit. The burner unit includes a burner and a first casing. The first casing houses the burner, and is provided with an air inlet. The heat exchange unit includes a heat exchanger, a second casing, and a connection portion. A flammable refrigerant passes through the heat exchanger. The second casing houses the heat exchanger. The connection portion is connected to a refrigerant connection pipe extending from a heat source unit. The first casing has a first surface. The second casing is disposed to overlap a part of the first surface. The first surface has a first portion that overlaps the second casing and a second portion that does not overlap the second casing. The connection portion is disposed on the second casing to be projected onto the second portion of the first casing. The air inlet is provided in a surface that is other than the second portion and is at least one of a plurality of surfaces adjacent to the first surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating an arrangement of an air conditioning system according to an embodiment of the present disclosure.

FIG. 2 is a schematic configuration diagram of the air conditioning system.

FIG. 3 is an external perspective view of an indoor unit.

FIG. 4 is an external perspective view of an indoor unit according to a first modification.

FIG. 5 is an external perspective view of an indoor unit according to a second modification.

FIG. 6 is an external perspective view of an indoor unit according to a third modification.

FIG. 7 is an external perspective view of an indoor unit according to a fourth modification.

FIG. 8 is an external perspective view of an indoor unit according to a fifth modification.

DESCRIPTION OF EMBODIMENTS

(1) Configuration of Air Conditioning System 1

FIG. 1 is a schematic view illustrating an arrangement of an air conditioning system 1 according to an embodiment of the present disclosure. FIG. 2 is a schematic configuration diagram of the air conditioning system 1. In FIGS. 1 and 2 , the air conditioning system 1 is a device used for air conditioning of a house or a building.

Here, the air conditioning system 1 is installed in a two-story house 200. In the house 200, rooms 201 and 202 are provided on the first floor, and rooms 203 and 204 are provided on the second floor. The house 200 is provided with a basement 205.

As illustrated in FIG. 2 , the air conditioning system 1 is a so-called duct air conditioning system. The air conditioning system 1 includes a utilization-side unit 50, a heat source-side unit 30, refrigerant connection pipes 36 and 37, and a duct 19 that sends air conditioned by the utilization-side unit 50 to the rooms 201 to 204.

The duct 19 includes an air supply duct 19 a and a return duct 19 b. The air supply duct 19 a is branched into the rooms 201 to 204, and is connected to ventilation ports 201 a to 204 a of the respective rooms 201 to 204. The return duct 19 b is branched into the rooms 201 to 204, and is connected to ventilation ports 201 b to 204 b of the respective rooms 201 to 204.

A substantially equal volume of air to a volume of air supplied from the utilization-side unit 50 to the rooms 201 to 204 through the air supply duct 19 a returns to the utilization-side unit 50 through the return duct 19 b.

For convenience of description, the utilization-side unit 50, the heat source-side unit 30, and the refrigerant connection pipes 36 and 37 are collectively referred to as an air conditioner 3.

In FIG. 2 , the utilization-side unit 50, the heat source-side unit 30, and the refrigerant connection pipes 36 and 37 constitute a heat pump unit 60 that heats a room by a vapor compression refrigeration cycle.

The air conditioning system 1 further includes a gas furnace unit 20 as a separate heat source from the heat pump unit 60. The gas furnace unit 20 heats the room by heat generated by gas combustion.

The air conditioning system combining the heat pump unit 60 and the gas furnace unit 20 can perform the heat pump heating operation by the heat pump unit 60 at a relatively high outside air temperature, and perform the heating operation by the gas furnace unit 20 at a low outside air temperature. It is also possible to provide a safer device when using a flammable refrigerant having a small global warming potential (GWP).

Therefore, the air conditioning system having a low global warming effect can be used not only in an area where the outside air temperature is relatively high but also in an area where the outside air temperature is low.

For convenience of description, a unit including the utilization-side unit 50 and the gas furnace unit 20 is referred to as the indoor unit 2.

(2) Indoor Unit 2

FIG. 3 is an external perspective view of the indoor unit 2. In FIG. 3 , the gas furnace unit 20 is housed in a first casing 11. The utilization-side unit 50 is housed in a second casing 41.

The first casing 11 has a first surface 111. The second casing 41 is disposed to overlap a part of the first surface 111. As a result, the first surface 111 has a first portion 111 a that overlaps the second casing 41 and a second portion 111 b that does not overlap the second casing 41.

As illustrated in FIG. 3 , the first portion 111 a of the first surface 111 is open, and the first casing 11 and the second casing 41 communicate with each other inside.

The second casing 41 has a surface 411 adjacent to the second portion 111 b. The surface 411 is provided with a liquid pipe connection portion 38 and a gas pipe connection portion 39. The liquid pipe connection portion 38 is connected to the liquid refrigerant connection pipe 36 extending from the heat source-side unit 30. The gas pipe connection portion 39 is connected to the gas refrigerant connection pipe 37 extending from the heat source-side unit 30.

The liquid pipe connection portion 38 and the gas pipe connection portion 39 protrude outward to such an extent as to be projected onto the second portion 111 b.

An air inlet 11 a including a plurality of openings is provided in the first casing 11. The surface on which the air inlet 11 a is provided is a surface that is other than the second portion 111 b and is at least one of a plurality of surfaces adjacent to the first surface 111. Here, being adjacent means being in a positional relationship of forming a corner.

Here, the plurality of surfaces adjacent to the first surface 111 will be described. When the surface 411 on which the liquid pipe connection portion 38 and the gas pipe connection portion 39 are disposed is viewed as a front surface, the surface facing the first surface 111 of the first casing 11 is defined as a second surface 112.

Next, the surface located between the first surface 111 and the second surface 112 and forming a front surface is defined as a third surface 113.

The surfaces adjacent to both the first surface 111 and the third surface 113 are defined as a fourth surface 114 and a fifth surface 115, respectively.

In the present embodiment, as illustrated in FIG. 3 , the third surface 113 is provided with the air inlet 11 a.

As illustrated in FIG. 2 , the utilization-side unit 50 includes a blow-out air temperature sensor 43 and an indoor temperature sensor 14.

The indoor temperature sensor 14 detects a temperature (hereinafter referred to as an indoor temperature Tr) of air in the air inlet 11 a of the first casing 11. The indoor temperature sensor 14 may be provided in one of the rooms 201 to 204 instead of the indoor unit 2.

A gas sensor 90 is installed in the indoor unit 2. When a refrigerant leaks from the refrigerant circuit 61 of the heat pump unit 60, the gas sensor 90 detects leaking refrigerant, outputs a detection signal to a controller 80, and the indoor fan 24 is driven to agitate the leaking refrigerant. The refrigerant sealed in the refrigerant circuit 61 is a flammable refrigerant, and R32 is used in the present embodiment.

(3) Details of Heat Pump Unit 60

In the heat pump unit 60 of the air conditioner 3, the utilization-side unit 50 and the heat source-side unit 30 are connected to each other via the refrigerant connection pipes 36 and 37 to constitute the refrigerant circuit 61. The refrigerant connection pipes 36 and 37 are refrigerant pipes constructed on-site when the air conditioner 3 is installed.

(3-1) Utilization-Side Unit 50

The utilization-side unit 50 is installed in the basement 205 of the house 200. Note that an installation location of the utilization-side unit 50 is not necessarily the basement 205, and may be installed at another indoor place. The utilization-side unit 50 includes an indoor heat exchanger 40 as a refrigerant radiator that heats air through heat radiation from a refrigerant, and an indoor expansion valve 42.

(3-1-1) Indoor Heat Exchanger 40

The indoor heat exchanger 40 is disposed on a most leeward side of a ventilation path from the air inlet 11 a to an air outlet 44 in the first casing 11.

(3-1-2) Indoor Expansion Valve 42

During a cooling operation, the indoor expansion valve 42 decompresses the refrigerant circulating in the refrigerant circuit 61, and causes the refrigerant to flow through the indoor heat exchanger 40. Here, the indoor expansion valve 42 is a decompression valve connected to a liquid side of the indoor heat exchanger 40.

(3-2) Heat Source-Side Unit 30

The heat source-side unit 30 is installed outside of the house 200. The heat source-side unit 30 includes a compressor 31, an outdoor heat exchanger 33, an outdoor expansion valve 34, and a four-way switching valve 32.

(3-2-1) Compressor 31

The compressor 31 is a hermetic compressor that houses, in a casing, a compression element (not shown) and a compressor motor 31 a that rotationally drives the compression element.

The compressor motor 31 a is supplied with electric power via an inverter device (not shown), and allows an operating capacity to be varied by changing a frequency (a number of revolutions) of the inverter device.

(3-2-2) Outdoor Heat Exchanger 33

The outdoor heat exchanger 33 functions as a refrigerant evaporator that evaporates the refrigerant. Near the outdoor heat exchanger 33, an outdoor fan 35 that sends outdoor air to the outdoor heat exchanger 33 is provided. In the outdoor fan 35, a fan 35 a is rotationally driven by an outdoor fan motor 35 b.

(3-2-3) Outdoor Expansion Valve 34

During a heating operation, the outdoor expansion valve 34 decompresses the refrigerant circulating in the refrigerant circuit 61, and causes the refrigerant to flow through the outdoor heat exchanger 33. Here, the outdoor expansion valve 34 is a decompression valve connected to a liquid side of the outdoor heat exchanger 33. The heat source-side unit 30 is provided with an outdoor temperature sensor 83 that detects a temperature of outdoor air outside of the house 200 where the heat source-side unit 30 is disposed (hereinafter referred to as an outside air temperature Ta).

(3-2-4) Four-Way Switching Valve 32

The four-way switching valve 32 is a valve to switch a refrigerant flow direction. During a cooling operation, the four-way switching valve 32 connects a discharge side of the compressor 31 and a gas side of the outdoor heat exchanger 33 to each other, and also connects a suction side of the compressor 31 and a gas refrigerant connection pipe 37 to each other (a cooling operation state: see a solid line of the four-way switching valve 32 in FIG. 2 ). As a result, the outdoor heat exchanger 33 functions as a refrigerant condenser, and the indoor heat exchanger 40 functions as a refrigerant evaporator.

During a heating operation, the four-way switching valve 32 connects a discharge side of the compressor 31 and the gas refrigerant connection pipe 37 to each other, and also connects a suction side of the compressor 31 and a gas side of the outdoor heat exchanger 33 to each other (a heating operation state: see a broken line of the four-way switching valve 32 in FIG. 2 ). As a result, the indoor heat exchanger 40 functions as a refrigerant condenser, and the outdoor heat exchanger 33 functions as a refrigerant evaporator.

(4) Details of Gas Furnace Unit 20

The gas furnace unit 20 is provided in the first casing 11 located below the second casing 41. The gas furnace unit 20 is a gas combustion heating device, and includes a combustion unit 10, a fuel gas valve 12, a furnace fan 13, a furnace heat exchanger 15, an air supply pipe 16, and an exhaust pipe 17.

(4-1) Combustion Unit 10

The combustion unit 10 is a device that obtains high-temperature combustion gas by burning mixed gas of fuel gas and air with a gas burner or the like (not shown).

(4-2) Fuel Gas Valve 12

The fuel gas valve 12 is configured by an electromagnetic valve or the like controlled to open and close, and is provided in a fuel gas supply pipe 18 extending from outside of the first casing 11 to the combustion unit 10. As the fuel gas, natural gas, petroleum gas, and the like are used.

(4-3) Furnace Fan 13

The furnace fan 13 is a fan that generates an air flow of taking in air into the combustion unit 10 through the air supply pipe 16, then sending the air to the furnace heat exchanger 15, and discharging from the exhaust pipe 17. In the furnace fan 13, a fan 13 a is rotationally driven by a furnace fan motor 13 b.

(4-4) Furnace Heat Exchanger 15

The furnace heat exchanger 15 is a heat exchanger that heats air by heat radiation from the combustion gas obtained in the combustion unit 10, and functions as a separate heat source radiator that heats air by heat radiation from a heat source (here, heat from gas combustion) that is separate from the heat pump unit 60.

The furnace heat exchanger 15 is disposed on a windward side of the indoor heat exchanger 40 in the ventilation path from the air inlet 11 a to the air outlet 44 in the first casing 11.

(4-5) Indoor Fan 24

The indoor fan 24 takes air into the first casing 11, and supplies air heated by the indoor heat exchanger 40 of the heat pump unit 60 or the furnace heat exchanger 15 of the gas furnace unit 20 into the rooms 201 to 204.

In the ventilation path from the air inlet 11 a to the air outlet 44 in the first casing 11, the indoor fan 24 is disposed on a windward side of both the indoor heat exchanger 40 and the furnace heat exchanger 15. The indoor fan 24 includes a fan 24 a and an indoor fan motor 24 b that rotationally drives the fan 24 a

(5) Controller 80

The utilization-side unit 50 is equipped with an indoor-side control board 81 that controls an operation of each part of the utilization-side unit 50. The heat source-side unit 30 is equipped with an outdoor-side control board 82 that controls an operation of each part of the heat source-side unit 30. Then, the indoor-side control board 81 and the outdoor-side control board 82 have a microcomputer or the like, and transmit or receive control signals or the like with a thermostat 70. The control signals are not transmitted or received between the indoor-side control board 81 and the outdoor-side control board 82. A control device including the indoor-side control board 81 and the outdoor-side control board 82 is called a controller 80.

(6) Basic Operation of Air Conditioning System 1

An air conditioning operation of the air conditioning system 1 includes a fan operation, a cooling operation, and a heating operation. Here, a basic operation of the heating operation will be described with reference to FIGS. 1 and 2 . The heating operation of the air conditioning system 1 includes a heat pump heating operation for heating a room with the heat pump unit 60, and a separate heat source heating operation for heating a room with the gas furnace unit 20.

(6-1) Heat Pump Heating Operation

During the heat pump heating operation, the refrigerant in the refrigerant circuit 61 is suctioned into the compressor 31, and compressed to become a high-pressure gas refrigerant. This high-pressure gas refrigerant is sent from the heat source-side unit 30 to the utilization-side unit 50 via the gas refrigerant connection pipe 37.

The high-pressure gas refrigerant sent to the utilization-side unit 50 is sent to the indoor heat exchanger 40. The high-pressure gas refrigerant sent to the indoor heat exchanger 40 is cooled by heat exchange in the indoor heat exchanger 40 with indoor air F1 (F2) supplied by the indoor fan 24, to be condensed to become a high-pressure liquid refrigerant.

This high-pressure refrigerant is sent from the utilization-side unit 50 to the heat source-side unit 30 via the indoor expansion valve 42 and the liquid refrigerant connection pipe 36. Whereas, indoor air F3 heated in the indoor heat exchanger 40 is sent from the utilization-side unit 50 to the rooms 201 to 204 through the duct 19, for heating.

The high-pressure liquid refrigerant sent to the heat source-side unit 30 is sent to the outdoor expansion valve 34, and decompressed by the outdoor expansion valve 34 to become a low-pressure refrigerant in a gas-liquid two-phase state. This low-pressure refrigerant in the gas-liquid two-phase state is sent to the outdoor heat exchanger 33.

The low-pressure refrigerant in the gas-liquid two-phase state sent to the outdoor heat exchanger 33 is heated by heat exchange in the outdoor heat exchanger 33 with outdoor air supplied by the outdoor fan 35, to evaporate to become a low-pressure gas refrigerant. This low-pressure gas refrigerant is suctioned into the compressor 31 again.

Then, in the heat pump heating operation described above, an outdoor-side microcomputer 82 a of the controller 80 controls the indoor temperature Tr in the rooms 201 to 204 to reach a set temperature (hereinafter referred to as an indoor set temperature Ts), by controlling an operating capacity Gr of the compressor 31 and by controlling of an opening degree of the outdoor expansion valve 34 (hereinafter referred to as an opening degree V).

(6-2) Separate Heat Source Heating Operation

During the separate heat source heating operation, the fuel gas valve 12 is opened to supply fuel gas to the combustion unit 10. The fuel gas is mixed with air taken in from the air supply pipe 16 by the furnace fan 13 in the combustion unit 10. The mixed gas of the fuel gas and the air is ignited and burned to generate high-temperature combustion gas.

The high-temperature combustion gas generated in the combustion unit 10 is sent to the furnace heat exchanger 15 as a separate heat source radiator. The high-temperature combustion gas sent to the furnace heat exchanger 15 is cooled by heat exchange in the furnace heat exchanger 15 with the indoor air F1 supplied by the indoor fan 24, to become low-temperature combustion gas. This low-temperature combustion gas is discharged from the gas furnace unit 20 via the exhaust pipe 17. Whereas, the indoor air F2 (F3) heated in the furnace heat exchanger 15 is sent from the utilization-side unit 50 to the rooms 201 to 204 through the duct 19, for heating.

Then, in the separate heat source heating operation described above, an indoor-side microcomputer 81 a of the controller 80 controls the indoor temperature Tr in the rooms 201 to 204 to reach the indoor set temperature Ts, by controlling opening and closing of the fuel gas valve 12.

The indoor-side microcomputer 81 a of the controller 80 performs control to open the fuel gas valve 12 when a temperature difference obtained by subtracting the indoor set temperature Ts from the indoor temperature Tr becomes large, and the indoor-side microcomputer 81 a performs control to close the fuel gas valve 12 when the temperature difference becomes small.

(6-3) Switching Operation Between Heat Pump Heating Operation and Separate Heat Source Heating Operation

In the air conditioning system 1, when the outside air temperature Ta is significantly low, the heat pump heating operation may not be able to cover an air conditioning load (a heating load) in a room (here, the rooms 201 to 204). Therefore, the heat pump heating operation is switched to the separate heat source heating operation in accordance with a decrease in the outside air temperature Ta. On the contrary, the separate heat source heating operation is switched to the heat pump heating operation in accordance with an increase of the outside air temperature Ta.

When an operation of the air conditioning system 1 starts, first, the heat pump heating operation is performed. Then, when the outside air temperature Ta during the heat pump heating operation reaches a first temperature Ta1 or less, and a heating capacity of the heat pump unit 60 reaches an upper limit, the heat pump heating operation is switched to the separate heat source heating operation.

Note that, whether an operating capacity of equipment included in the heat pump unit 60 has reached the upper limit is determined by whether a number N of revolutions of the compressor motor 31 a has reached an upper limit number Nu of revolutions, and/or whether the opening degree V of the outdoor expansion valve 34 has reached an upper limit opening degree Vu.

Whereas, in the separate heat source heating operation, the separate heat source heating operation is switched to the heat pump heating operation when the outside air temperature Ta during the separate heat source heating operation reaches a second temperature Ta2 or higher.

(7) Characteristics

In the above embodiment, as illustrated in FIG. 3 , the air inlet 11 a provided in the third surface 113 of the first casing 11 reduces a risk that the combustion unit 10 serves as an ignition source of the flammable refrigerant R32.

This is because the surface provided with the air inlet 11 a is the third surface 113 among the plurality of surfaces adjacent to the first surface 111, rather than the second portion 111 b of the first surface 111 which is the surface closest to the liquid pipe connection portion 38 and the gas pipe connection portion 39 in the first casing 11 housing the combustion unit 10.

(8) Modifications

The position or shape of the air inlet 11 a may be changed to further reduce the risk that the combustion unit 10 serves as an ignition source of the flammable refrigerant R32.

(8-1) First Modification

FIG. 4 is an external perspective view of the indoor unit 2 according to a first modification. In FIG. 4 , a difference between the embodiment and the first modification is that a height position of the air inlet 11 a is located vertically lower in the first modification than in the embodiment.

As illustrated in FIG. 4 , the air inlet 11 a is provided at a position closer to an end farther from the second casing 41 than an end closer to the second casing 41.

Since a concentration of the refrigerant gas decreases as a distance from a leakage point increases, by providing the air inlet 11 a of the first casing 11 at a position closer to the end farther from the second casing 41 than the end closer to the second casing 41, the risk that the combustion unit 10 serves as an ignition source of the flammable refrigerant R32 is further reduced.

(8-2) Second Modification

FIG. 5 is an external perspective view of the indoor unit 2 according to a second modification. In FIG. 5 , a difference between the embodiment and the second modification is that the shape of the air inlet 11 a differs.

As illustrated in FIG. 5 , the air inlet 11 a is the same as the first modification in that the air inlet 11 a includes a plurality of openings, but each opening has a slit shape extending in a direction away from the first surface 111.

If the refrigerant leaks from the liquid pipe connection portion 38 and the gas pipe connection portion 39, the refrigerant flows down along the surface 411 and then flows downward along a surface of the first casing 11. Therefore, when the refrigerant is sucked from the air inlet 11 a toward the combustion unit 10 by the indoor fan 24, it is considered that a risk that the refrigerant is sucked into a longitudinal slit parallel to a direction of a refrigerant flow is lower than into a lateral slit orthogonal to the refrigerant flow.

(8-3) Third Modification

FIG. 6 is an external perspective view of the indoor unit 2 according to a third modification. In FIG. 6 , a difference between the embodiment and the third modification is that the surface on which the air inlet 11 a is provided is not the third surface 113, but is provided on the fourth surface 114 or the fifth surface 115 among the plurality of surfaces adjacent to the first surface 111.

If the refrigerant leaks from the liquid pipe connection portion 38 and the gas pipe connection portion 39, the refrigerant may flow down along the surface 411 and then flow down along the third surface 113 of the first casing 11 parallel to the surface 411. The air inlet 11 a, which is provided not on the third surface 113 parallel to the surface 411 provided with the liquid pipe connection portion 38 and the gas pipe connection portion 39 but on the fourth surface 114 and the fifth surface 115 orthogonal to the surface 411, further reduces the risk of the refrigerant being sucked.

(8-4) Fourth Modification

FIG. 7 is an external perspective view of the indoor unit 2 according to a fourth modification. In FIG. 7 , a difference between the embodiment and the fourth modification is that the embodiment is a vertical type in which the first casing 11 and the second casing 41 are disposed in the vertical direction, while the fourth embodiment is a horizontal type in which the first casing 11 and the second casing 41 are horizontally laid down.

Thus, since devices and components used are basically the same, the same names and the same reference signs as those in the embodiment are given to devices and components, and detailed description thereof will be omitted.

In the horizontal type, when the surface 411 on which the liquid pipe connection portion 38 and the gas pipe connection portion 39 are disposed is viewed as a front surface, the first casing 11 has the second surface 112 facing the first surface 111, the third surface 113 located between the first surface 111 and the second surface 112 and defined as a front surface, and the fourth surface 114 and the fifth surface 115 adjacent to both the first surface 111 and the third surface 113.

As illustrated in FIG. 7 , the surface on which the air inlet 11 a is provided is provided on the fourth surface 114 among a plurality of surfaces adjacent to the first surface 111.

Each opening of the air inlet 11 a has a slit shape, and a longitudinal direction of each opening extends from the first casing 11 toward the second casing 41.

In the horizontal type, if the refrigerant leaks from the liquid pipe connection portion 38 and the gas pipe connection portion 39, it is considered that the refrigerant is retained near a floor surface and the concentration of the refrigerant becomes high near the floor surface, since the refrigerant has a larger specific gravity than air.

The air inlet 11 a, which is provided on the fourth surface 114 and is thus located on the surface farthest from the floor surface among the surfaces constituting the first casing 11, further reduces the risk of the refrigerant being sucked.

In the fourth modification, as can be seen from FIG. 7 , the liquid pipe connection portion 38 and the gas pipe connection portion 39 are located closer to the second portion 111 b of the first surface 111 than in the embodiment. Between the liquid pipe connection portion 38 and the gas pipe connection portion 39, and the third surface 113, the second portion 111 b of the first surface 111 serves as a vertical wall. Therefore, if the refrigerant leaks from the liquid pipe connection portion 38 and the gas pipe connection portion 39, movement of the refrigerant to the third surface 113 and the fourth surface 114 is inhibited, and the risk of the refrigerant being sucked is further reduced.

(8-5) Fifth Modification

FIG. 8 is an external perspective view of the indoor unit 2 according to a fifth modification. In FIG. 8 , the fifth modification is a further modification of the fourth modification.

In the horizontal type of the fourth modification, if the refrigerant leaks from the liquid pipe connection portion 38 and the gas pipe connection portion 39, it is considered that the concentration of the refrigerant becomes high near the floor surface since the refrigerant has a larger specific gravity than air, and thus the air inlet 11 a is provided on the fourth surface 114 farthest from the floor surface.

However, as can be seen from FIGS. 7 and 8 , the second portion 111 b of the first surface 111 serves as a vertical wall between the liquid pipe connection portion 38 and the gas pipe connection portion 39, and the third surface 113. Therefore, if the refrigerant leaks from the liquid pipe connection portion 38 and the gas pipe connection portion 39, movement of the refrigerant to the third surface 113 is inhibited.

Accordingly, as illustrated in FIG. 8 , although the air inlet 11 a is provided not only on the fourth surface 114 but also on the third surface 113, the risk of the refrigerant being sucked can be suppressed.

As illustrated in FIG. 8 , the air inlet 11 a includes a plurality of openings, each opening has a slit shape, and a longitudinal direction of each opening extends from the first casing 11 toward the second casing 41, as in the fourth modification.

However, since the air inlet 11 a is arranged in a row from the third surface 113 to the fourth surface 114 in the fifth modification, the air inlet 11 a is separated from the second portion 111 b of the first surface 111 as compared with in the fourth modification, and the risk of the refrigerant being sucked is further suppressed.

(9) Other Embodiments

In the embodiment and the modifications, the air conditioning system combining a heat pump capable of heating and cooling and a furnace is taken as an example, but the present disclosure is not limited thereto.

For example, the air conditioning system may be an air conditioning system combining an air conditioner dedicated to cooling and a furnace.

Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure described in claims.

EXPLANATION OF REFERENCE

-   -   1: air conditioning system     -   10: combustion unit (burner)     -   11: first casing     -   11 a: air inlet     -   20: gas furnace unit (burner unit)     -   30: heat source unit     -   36: liquid refrigerant connection pipe (refrigerant connection         pipe)     -   37: gas refrigerant connection pipe (refrigerant connection         pipe)     -   38: liquid pipe connection portion     -   39: gas pipe connection portion     -   40: indoor heat exchanger (heat exchanger)     -   41: second casing     -   50: utilization-side unit (heat exchanger unit)     -   111: first surface     -   111 a: first portion     -   111 b: second portion     -   112: second surface     -   113: third surface     -   114: fourth surface     -   115: fifth surface

CITATION LIST Patent Literature

-   Patent Literature 1: JP 2015-145764 A 

1. An air conditioning system comprising: a burner unit including a burner and a first casing that houses the burner and has an air inlet; and a heat exchanger unit including a heat exchanger through which a flammable refrigerant passes, a second casing that houses the heat exchanger, and a connection portion connected to a refrigerant connection pipe extending from a heat source unit, wherein the first casing has a first surface, the second casing is disposed to overlap a part of the first surface, the first surface includes a first portion that overlaps the second casing and a second portion that does not overlap the second casing, the connection portion is disposed in the second casing to be projected onto the second portion of the first casing, and the air inlet is provided on a surface that is other than the second portion and is at least one of a plurality of surfaces adjacent to the first surface.
 2. The air conditioning system according to claim 1, wherein the air inlet is provided at a position closer to an end farther from the second casing than an end closer to the second casing on at least one of the plurality of surfaces adjacent to the first surface.
 3. The air conditioning system according to claim 1, wherein the air inlet has a plurality of openings, and each of the plurality of openings has a slit shape extending in a direction away from the first surface.
 4. The air conditioning system according to claim 1, wherein when a surface on which the connection portion is disposed is viewed as a front surface, the first casing further includes a second surface facing the first surface, a third surface located between the first surface and the second surface and defined as a front surface, and a fourth surface and a fifth surface adjacent to both the first surface and the third surface, and the air inlet is provided in at least one of the fourth surface or the fifth surface.
 5. The air conditioning system according to claim 1, wherein when a surface on which the connection portion is disposed is viewed as a front surface, the first casing further includes a second surface facing the first surface, a third surface located between the first surface and the second surface and defined as a front surface, and a fourth surface and a fifth surface adjacent to both the first surface and the third surface, and the air inlet is provided in the third surface and in the fourth surface or the fifth surface. 